


The Origin of a New Species

by ArwaMachine



Category: Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Established Relationship, Established Sherlock Holmes/John Watson, Fluff and Smut, Hand Jobs, Kissing, M/M, Plot What Plot/Porn Without Plot, Porn with Feelings, Slash
Language: English
Status: Completed
Published: 2020-07-07
Updated: 2020-07-07
Packaged: 2021-03-04 21:53:58
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,376
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25133455
Author URL: https://archiveofourown.org/users/ArwaMachine/pseuds/ArwaMachine
Summary: Sherlock hadn’t had a case—not a case worth chasing, anyway—in over four billion years and everything was so mind-numbingly boring that he had devolved. This just sort of happened from time to time.John can help.
Relationships: Sherlock Holmes & John Watson, Sherlock Holmes/John Watson
Comments: 47
Kudos: 178
Collections: Sherlock Author Showcase 2020





	The Origin of a New Species

Sherlock was a single-celled organism.

This just sort of happened from time to time.

He lay on the sofa in the sitting room, staring at the ceiling without really seeing it, motionless and purposeless and thoughtless. It was unclear how long he had been there—forever, perhaps. John had gone out an undetermined time ago and the flat was still and silent and it would all be quite dreadful were Sherlock not a single-celled organism.

Sherlock hadn’t had a case—not a case worth chasing, anyway—in over four billion years and everything was so mind-numbingly boring that he had devolved, or perhaps had never even evolved in the first place. He couldn’t quite remember. His mobile was silent and the website was dead and everything had sunk into a stupor, the oxygen draining from the flat and reducing Sherlock to little more than a prokaryote. He was formless, so light as to be weightless, supported only by the dull leather of the sofa beneath him as the thing that may once have been his body sunk into nothingness and the things that may once have been his eyes stared at the ceiling. He didn’t have bones anymore. He didn’t have eyes. He was no longer terrestrial. He floated in water, the world thick and slow around him. His lungs were gone, he didn’t breathe anymore. He took in what little oxygen was left in the flat through diffusion, absorbing it into his skin without effort or thought. Everything was slow, agonizingly slow, too slow to be meaningful. At a certain point, everything drops down to zero. To say that Sherlock still existed was a bit of an exaggeration.

It was awfully dull, but when you’re a single-celled organism you find that you don’t much care.

If Sherlock still had ears with an eardrum and a cochlea and a basilar membrane and an auditory nerve he would have heard the front door close and footsteps plod their way up the stairs. If he still had a temporal lobe and a limbic system and a hippocampus he would have recognized the footsteps as belonging to John. But he didn’t have any of those things, being a single-celled organism and all, so he neither heard nor recognized John as he entered the flat.

“Still on the sofa, I see.”

Sherlock didn’t respond. He didn’t even turn his head towards the sound. It was possible he didn’t even blink. He didn’t need to blink—he was a water-dwelling creature. John’s voice could barely be heard through the murk surrounding him, a muffled echo that may or may not have just been Sherlock’s imagination, if he had one of those anymore. It was difficult to tell. The water was thick and heavy and Sherlock had to do very little to survive in it.

“No new cases, then?”

If Sherlock had lips he would have frowned. If he had lungs he would have sighed. If he had language he would have spoken. As it turned out, he didn’t have any of those things. So instead, he floated on, lost at the bottom of the bog.

This was the way of it when there wasn’t a case on and hadn’t been for eons and the mental stagnation that crashed into the flat was a cataclysmic event resulting in mass extinction. Everything reverted back to nothing. Organisms couldn’t adapt after the apocalypse. The planet was no longer life-sustaining. These things just sort of happened. John understood, or at least he tried to.

Sherlock used to be a complex life form, so far as he could recall, which was not particularly far. He used to be brilliant and brazen and remarkable and made of multitudes. He used to be the cataclysmic event in this flat, breaking all things down to their constituent parts, reducing everything to zero. Cases. Criminals. Chemicals. John.

He used to be able to wrest John’s DNA from his body with ease, taking the microscopic bits of code that wove together the fabric of John and swallow them down like a sip of tea. Like a god, consuming life.

Or at least, he thought he was once able to do these things, but he was having trouble remembering. One of the side effects of not having a brain.

John stood over him, arms crossed over his chest. John wasn’t a single-celled organism, not in the literal sense, anyway. He still had arms that folded and a chest that expanded and a mouth that twisted at its side and eyes that looked down at him with a hint of crystal concern.

“You haven’t moved all day.”

 _I’m a single-celled organism_ , Sherlock thought. _We do very little_. He couldn’t speak those words of course—no language and all—but he made a little noise, a grunt of sorts, which he thought was quite impressive for his current stage of evolutionary development.

John sighed and walked over to the laptop that Sherlock left sitting on the desk back when he was capable of complex motor functions. John lifted the lid and tapped at some buttons. He leaned against the desk, the weight of his body resting against his right palm as his left scrolled through something or other on the computer. His brow furrowed. He frowned. So many voluntary movements, so many muscle groups activated. How lucky John was.

“What about this one?” John asked. “Woman saying someone broke into her flat and only nicked her salad forks and several pairs of shoes.”

Sherlock said nothing. He carried on not really existing.

John waited out the silence for a moment. “Right,” he said, scrolling further. “How’s this? Brother gone missing. Left behind a note that said _bring Steve_. Something there, right?” He looked up at Sherlock, face hopeful. A complicated bit of emotion, hope.

Sherlock made another little noise. He was really on a roll with these little noises.

“Okay,” John said. “Here. Man says his dog has been—” John hung his head, not even bothering to finish his sentence. “Fine. You’re right. These are all rubbish.”

Sherlock used to be right all the time, about so many things. He used to love when John admitted it. He used to turn into a bioluminescent being whenever John smiled at him, called him _brilliant amazing extraordinary_. Single-celled organisms don’t require much praise. They don’t do anything particularly spectacular except not be dead. Sherlock could, at least, do that much. But only barely.

“Well,” John was saying. “We at least need to get you moving. Get you out of the flat. Maybe a walk in Regent’s Park.”

Walking was too complex a task. It required multiple cells, for starters, to construct bones and joints and muscles and nerves. It required legs with long bones, flexible knees, and broad hips to manage stress and impact. It required a spine, preferably a curved spine to absorb shock, to carry messages to muscles. It required a skull, one positioned upright on his body and containing some sort of brain with a motor cortex to control the entire ordeal. All of this, of course, was countless stages of development away from where Sherlock currently lay on the evolutionary flowchart. Walking was right out.

“Have you showered today, at least?”

Seeing as Sherlock was a water-dwelling prokaryote, showering seemed redundant and wholly unnecessary.

“When did you last eat?”

Sherlock didn’t need to eat. He absorbed nutrients from the surrounding environment. It was convenient. It didn’t provide him with much energy, but it didn’t require much energy either. He saw it as a win-win.

“Sherlock?”

John had moved back towards the sofa, exercising his abilities as a bipedal animal. He stood in front of Sherlock, positioning himself between the coffee table and Sherlock’s potentially nonexistent body, hands on his hips.

“Are you even listening to me?”

It might have been a shift in the tide, but Sherlock’s head lolled to the side to point at John. John looked concerned but not overly so; he had studied Sherlock’s evolutionary progression before and was becoming something of an expert. John was wearing a dark jumper and a pair of faded jeans that the Sherlock who used to have a frontal lobe would know were over a decade old apiece, but at the moment looked much smarter than Sherlock, whose non-body was covered in the same pyjamas and dressing gown he had been wearing for four billion years. Clothes weren’t particularly meaningful for Sherlock’s state, and changing them was even less meaningful.

John sighed.

He stepped forward, heaving one leg over Sherlock’s waist and climbing onto the sofa until he was straddling Sherlock’s thighs. His fingers drifted across Sherlock’s shoulders, down the sides of his arms. Sherlock might even have felt it, if he still had nerve endings. If any of the aforementioned body parts still existed.

“A bit catatonic today, are we?” John asked. His eyes were the color of water. He hovered over Sherlock, shining down at him like the sun. Sherlock could feel himself sucking John in, absorbing his light, feeding on him like photosynthesis, taking what John gave and turning into something greater. Sherlock’s lone cell twitched.

A ripple in the water moved what used to be Sherlock’s hands to John’s legs. His fingers followed the current and drifted along John’s calves, the curve of his legs, up onto his thighs. He was warm, like sunlight.

John planted a hand on the sofa beside what used to be Sherlock’s head. “You’re in there,” he said, leaning forward, the glow of his head moving ever closer. “I’ll find you.”

But Sherlock wasn’t lost, he was here—there just wasn’t much to him anymore. He could be defined so easily, by just a smattering of words. John was a dictionary. He was more complex than Sherlock could fathom.

John’s free hand came to rest on the side of Sherlock’s face, fingers grazing skin, transmitting energy. His fingertips brushed against the pili-like stubble darkening Sherlock’s cheek, binding him to the surface, facilitating movement. Cells move, Sherlock thought, when it is time to feed, when absorbing molecules from the surrounding atmosphere no longer satisfies, when one must find an unassuming life on which to prey. Cells move then, to consume. They move slow and without a plan, but they move. John ran his thumb over Sherlock’s lips, slightly parted. Sherlock’s tongue sludged forward, nudging at the pad of John’s finger. He tasted like salt and life and meat. Sherlock was _hungry_.

John ran his tongue over his lip, the barest of movements.

John wilted forward—slowly, things move slowly underwater—and pressed his mouth to Sherlock’s. Soft, a leaf landing on the still surface of a lake. Sherlock’s lips were dry—he didn’t need to produce moisture underwater—and John was patient, barely moving his mouth at all, the skin of his lower lip sticking to Sherlock’s upper lip, tugging without demanding. Sherlock felt a puff of air escape from John’s nose, floating across his face like the thinnest of clouds. John had lungs. He took in oxygen. He expelled carbon dioxide. One day, he could help Sherlock breathe.

Sherlock’s lips parted.

John sank inside.

 _I’ll find you_ , John had said. He was looking.

John wasn’t a water-dwelling creature and he had found a way to produce his own moisture and his tongue was wet and hot against Sherlock’s, invading, seeking, tasting. The tide must be coming in because Sherlock’s hands had drifted from John’s legs to his hips, his sides, his shoulders. Sherlock had a mouth now and it was moving—against John, with John, because of John. Sherlock considered consumption—how one cell ingests another cell, a smaller cell, intending only to feed but finding that the smaller cell lives on and gives back, gives energy, gives light. The two carry on—a part of each other—two cells instead of one, life doubled in an instant. They fit together perfectly, working as if designed for each other from the start, each giving what the other requires, requiring what the other gives. The two cells benefit each other, they _need_ each other, they can’t survive without the other. The two together create something larger than themselves, something that builds and grows and takes over and _that_ was why he needed John. John could bring him back—he always brings him back. John always makes him better, better than before.

Sherlock had pieces to him now and he was expanding. He was developing proprioception, he could tell which end was up. He had a cranial end and John’s mouth was pressed to it, hungry, devouring. He had a caudal end and John had settled against it, sliding his legs downward and slotting himself between what, over time, would become Sherlock’s legs. He had a dorsal side and it was pressing into the sofa, weighted down by the firm force of John’s body on his, wrapped up in John’s arm, which had wound itself between the sofa and Sherlock’s shoulder. He had a ventral side and John was covering it like a layer of soil, sinking into him, filling his cracks, making him grow.

Sherlock must have sprung a spine because John’s mouth moved to his neck and it arched, bending him upwards, pressing him further into John’s body. He was growing bones, aching nubs of calcium, wrapping around his center like a shell and splitting from his corners to form limbs—four of them, perfect for swimming, for crawling. He barely had control over any of it and his newly-formed limbs flopped and floundered, wrapping themselves desperately around John, grasping at him, pulling him closer. John moved against him, a fierce, fluid movement, and Sherlock considered that bones were rough, much rougher than water, and everything had an urgency to it. Sherlock wasn’t formless or weightless or soft or slow anymore. Everything was growing, fast, _hard_.

John was saying something to him, or perhaps just articulating sounds against his ear, his neck, his collarbone. John’s hands were everywhere, charting the progression of growth along Sherlock’s newly-formed body. Sherlock was learning how to move, John was teaching him how to move, _making_ him move, they were moving together. John was buoyant, he floated. He brought Sherlock along, pulling him upwards, carrying him out of the depths of the water, closer to the light. John always brings him closer to the light, it’s what John does. Sherlock didn’t have eyes yet but he could still see it somehow—the light shining off John—and it was piercing and white and blinding and drawing him closer and closer and closer. There was so much light up there on the surface, and oxygen. Too much oxygen, and Sherlock didn’t know if he could breathe yet. It might hurt. But John was taking him to the surface and Sherlock was ready to feel something.

John shifted his weight to the side, nudging himself between Sherlock and the back of the sofa. He brought his hand to his mouth and ran his tongue along his palm. John could produce his own moisture. He was good like that. John’s hand moved down Sherlock’s body, seeking fingers sneaking underneath the waistband of Sherlock’s trousers and pushing lower still until John found him and wrapped his slick hand around Sherlock’s cock, squeezing and sliding along rigid flesh, and Sherlock’s diaphragm flexed and his ribs expanded and his mouth fell open and he broke through the surface tension of the water and sucked in a sharp gasp of air. He had lungs again and they were a burning frenzy. He wasn’t used to so much oxygen. He was gasping, shaking, dizzy.

“I’ve got you,” John whispered into the space where Sherlock’s gills would have been, if he still had gills. No need for such rudimentary organs anymore; he was _breathing_.

Sherlock didn’t yet have language—that would come later, much later—but he had sounds. Grunts and gasps and moans and the noises air made when brought into fresh lungs with violence. He spoke his noises against John’s skin—into his ear, against his hair, back to his mouth when John’s lips again found his. They were bobbing as if floating on waves but they weren’t in the water anymore, they were making their own rhythm. He writhed under John’s hand, grasping at John’s arms and feeling the muscles flex as John gripped him. Sherlock had muscles now too because they were tightening, straining against each stroke of John’s hand. He must have had skin as well because it was burning. He didn’t have to worry about drying out now that he was on land because he had learned to produce his own moisture—a fine sheen of sweat forming across his body, pooling on his temples and in the center of his chest.

Sherlock thought about hands—John’s hands, specifically. There are over thirty muscles in just one hand alone, and if Sherlock focused hard enough he was sure he could feel each muscle against him at the moment, pulling the corners of John’s hand into a fist around Sherlock’s cock, tensing, squeezing, gripping. Hands grip for two purposes—power and precision—and John was exercising both, clutching Sherlock within the palm of his hand with a fervent grip while moving with delicacy, using each minute shift in muscles, joints, fingers to touch him with shuddering specificity. The wire-thin tendons that spanned the length of John’s hand extended his fingers as they ran down the length of him and then flexed again, curling each digit as John’s forearm, bicep, shoulder, worked to move the machine of his hand up and down, up and down. The joints of John’s wrist twisted his grip around the head of Sherlock’s cock, the muscles of his hand clenching further, fingers sweeping along the sensitive skin. Hands are sensitive and John had thousands of nerve endings in his, cataloguing the slick sensation of Sherlock’s skin, each twitch and surge of his rigid member, the hard, protruding ridge of his glans, the thick veins that emerged along his shaft he stroked Sherlock faster, faster, faster.

John’s hands—his impossible, intricate hands—were all that was tethering Sherlock to this world, tugging him along, bringing him into a new state of being. It was foolhardy, perhaps, to trust something so delicate to something so strong, but John knew how to use his control well. He knew how to bend without breaking, twist without pain, squeeze without crushing. Sherlock, however, was uncontrolled. He thrust his hips upwards into John’s hands, moaning into John’s mouth, doing his best to communicate that he needed faster harder more. Not having language was terribly inconvenient in times like these. John understood, his lips tugging into a smile and a little puff of a chuckle escaping against Sherlock’s mouth. His grip tightened around Sherlock, speeding up, wrist twisting, muscles flexing, fingers moving, turning, pulsing. Sherlock made a sound like a whimper—what would have been a little lost noise of a new being surrounded by unfamiliar terrain, unsure of what to do, except Sherlock wasn’t lost and he wasn’t unsure and nothing was unfamiliar about the way John touched him; Sherlock knew exactly what he wanted and where he was going. John was coming with him.

“ _God_ ,” John moaned against Sherlock’s mouth.

This world—the world above the water—was warm, so warm, and Sherlock’s body burned, moments away from ignition. Everything was hot and slick and perfect and John was there, pulling him into this new land, into the heat. The disparate pieces of Sherlock’s new body were clumsily learning to coordinate, his heart stuttering madly, blood thundering in his ears, muscles seizing, limbs thrashing and clutching, fingers digging into John, into his arms, his back, his hair, lungs gasping air down a throat raw from disuse, and language—language, finally—John, John, _John_.

“ _John_ ,” Sherlock gasped, the only word he knew.

“Yes,” John breathed, and all thirty muscles of his hand fit together to flex and twist and squeeze and stroke Sherlock’s cock with fervor and it was another cataclysmic event, a life-ender. Everything dropped down to zero again and the world went black and light blotted out and for a moment there may have been another mass extinction, a reversion into nothingness. Then Sherlock blinked back into existence and he was thrashing on the sofa, arms wrapped around John and thrusting into his hand, head tipped to the heavens and _coming_ , coming so hard he glimpsed the stars.

“Christ,” John said. His voice was soft with astonishment. Seeing a new being spring into life wasn’t an everyday occurrence. It warranted a fair bit of awe.

John’s hand stayed on Sherlock, slick with come, sliding gently over his skin until Sherlock shuddered with sensitivity, raw and unused to the elements. Sherlock’s chest was still heaving, his heart still drumming as if under attack, but things were starting to still, his new body seeking out homeostasis, whatever that might mean in this world. Sherlock blew out one shaking breath, then another. Another. Slowing, returning. Breathing was essential for life on land, but it didn’t have to be hard.

Sherlock opened his eyes. Front-facing eyes, useful for depth perception. He tilted his head to the side, his eyes seeing, sending visual data through his optic nerve and into his occipital lobe where it could be processed, catalogued. He saw John’s face, so close it was nearly touching his. John’s graying hair was in a spiked disarray, his parted lips red and slightly swollen, his cheeks tinged pink and lifted in a smile, his breath still coming in a bit heavy through flared nostrils. It was a lovely sight. John’s eyes, the color of clear skies, looked back into Sherlock’s with recognition.

“There you are,” John said, his smile a greeting. “You’re back.”

Sherlock smiled in return, facial muscles turning his lips upwards, communicating emotion to the outside world, triggering a release of endorphins and reminding his brain that he was, in fact, very happy at the moment.

“Hello,” Sherlock said, despite the fact that he knew John, had known John since he was a single-celled organism floating in nothing, would go on knowing John after whatever upcoming cataclysmic event ended the both of them. Possibly longer.

“Hello,” John said. “I’ve missed you.”

Sherlock ran his fingers along the side of John’s smile. He lifted his head, pressing his mouth to John’s in a slow kiss. He had missed John as well, it would seem.

“So,” John said once they had parted again, shifting slightly to wipe his hand on his trousers. “You ready to try moving, then?

Sherlock nodded, his fingers still tracing the outline of John’s face, enjoying this perk of his recently-developed fine motor control.

“Good,” said John. “Because you,” he kissed at Sherlock’s hand, “need a shower.”

Sherlock chuckled. Laughter—that was new. He quite liked it.

Sherlock thought again about how two cells—against all probability and intentions of life—learn to live together, giving what the other requires, requiring what the other gives. The two cells stop being separate entities at a certain point and carry on as one, working in tandem, ensuring their mutual survival. Needing each other. It was happenstance how it all occurred, how by some chance an organism happened to find the only other living thing that could compliment it in such a way that it made the both of them better, creating a novel, unique life where there once was nothing. More romantic souls might have called the whole thing a miracle, but all Sherlock knew was that it was in tremendous contradiction to the odds and, for that, he ought to be overwhelmingly grateful.

“Come with me,” Sherlock said.

John nuzzled at Sherlock’s nose. “If you insist,” he said, pressing a soft kiss to Sherlock’s lips.

With a low grunt, John shifted off of Sherlock and lifted himself from the sofa, stretching his arms over his head, the bones in his back cracking, a disadvantage of walking upright. He turned back to Sherlock and reached out a hand to him. Sherlock grasped his hand—opposable thumbs, how useful—and John heaved him off the sofa, pulling him into standing. Sherlock’s feet shifted on the floor, feeling out his balance. His legs lodged a brief complaint at the sudden call to action and his head swum, little dots dancing in front of his eyes as his blood rearranged itself to acclimate to the sudden change in position. Standing upright was a momentous task. Sherlock blinked and after a moment the dots faded and his legs strengthened. He wriggled his toes. He was a regular bipedal creature—very advantageous for terrestrial living.

Sherlock wrapped an arm around John, resting his hand in the small of John’s back as he tilted his head downward, catching John’s mouth in his. John’s lips parted and he hummed into the kiss, running his hands along Sherlock’s sides and over his arse. Yes, Sherlock thought, standing erect had its benefits.

John was smiling when the kiss ended, looking up at Sherlock as if he, in all his imperfections, was still the culmination of a billion-year process of selection and refinement of every possible trait that led the two of them to stand in this room together—upright, forward-facing, beautifully symbiotic. Evolution wasn’t over though—it never is. There were always more steps to take to move forward; they would take them together. John turned, tugging at Sherlock’s hand, pulling him in the direction of the hallway, the loo, the next step in his progression. John glanced back over his shoulder with that look that was light and hope.

Sherlock stayed still for a moment, letting their joined hands stretch out between the two of them, linking them together. Sherlock considered how organisms are bound to one another, sometimes through tangible means—cell walls and membranes, bound hands and joined mouths, invitations to enter one’s body—sometimes through intangible means—complimentary niches, defined roles in fragile ecosystems, flat shares—and sometimes through means more intangible still—heartfelt declarations, knowing looks, love. The binding agents that persist after hands are dropped. Sherlock smiled.

Then he followed, taking his first steps as a multicellular creature emerging onto the uncertain land, journeying forward into the light.

**Author's Note:**

> Thanks for reading! This is my first fic, but--oh--do I have plans...
> 
> I have a Tumblr! Follow me - arwamachine.tumblr.com
> 
> I also have a Twitter (@ArwaMachine) and one day I might even understand it


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